Move CI jobs for draft PRs to contributor's personal forks of Mill

.github/ISSUE_TEMPLATE.md

@@ -2,3 +2,6 @@ Please don't open issues for questions, but ask in our Discussions forum at http
 
 Mill installations via `coursier` or `cs` are unsupported.
 
+Please open all PRs as drafts to avoid being bottlenecked by Mill CI, and only
+convert to ready for review once CI on your own fork is green. There will be a 
+PR status check linking your fork's commit/CI history for convenient viewing 

.github/workflows/draft-ci.yml

@@ -0,0 +1,34 @@
+name: Draft CI
+
+permissions: write-all
+on:
+  pull_request_target:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - ready_for_review
+
+jobs:
+  run:
+    runs-on: ubuntu-latest
+    permissions: write-all
+    steps:
+      - name: Debug Echos
+        run: |
+          echo ${{ github.event.action }}
+          echo ${{ github.event.action == 'ready_for_review' }}
+          echo "${{ github.event.pull_request.head.repo.html_url }}/commits/${{github.event.pull_request.head.ref}}"
+      - name: Create status
+        run: |
+          curl --request POST \
+          --url ${{ github.event.pull_request.statuses_url }} \
+          --header 'authorization: Bearer ${{ secrets.GITHUB_TOKEN }}' \
+          --header 'content-type: application/json' \
+          --data '{
+            "state": "${{(github.event.action != 'ready_for_review' && github.event.pull_request.draft) && 'pending' || 'success'}}",
+            "context": "Draft CI / link",
+            "target_url": ${{(github.event.action != 'ready_for_review' && github.event.pull_request.draft) && format('"{0}/commits/{1}"', github.event.pull_request.head.repo.html_url, github.event.pull_request.head.ref) || 'null'}},
+            "description": "${{(github.event.action != 'ready_for_review' && github.event.pull_request.draft) && 'use CI on your repo fork (link on right) until this PR is ready for review' || 'PR is ready for review, running CI in Mill repo'}}"
+            }' \
+          --fail-with-body

.github/workflows/publish-artifacts.yml

@@ -14,12 +14,6 @@ on:
       - '**'
   workflow_dispatch:
 
-# cancel older runs of a pull request;
-# this will not cancel anything for normal git pushes
-concurrency:
-  group: cancel-old-pr-runs-${{ github.workflow }}-${{ github.head_ref || github.run_id }}
-  cancel-in-progress: true
-
 jobs:
   publish-sonatype:
     # when in master repo, publish all tags and manual runs on main

.github/workflows/run-tests.yml

@@ -11,28 +11,33 @@ name: Run Tests
 
 on:
   push:
-    branches:
-      - main
   pull_request:
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - ready_for_review
   workflow_dispatch:
 
 # cancel older runs of a pull request;
 # this will not cancel anything for normal git pushes
 concurrency:
-  group: cancel-old-pr-runs-${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  group: cancel-old-pr-runs-${{ github.workflow }}-${{ github.ref_name }}
   cancel-in-progress: true
 
 jobs:
   # Jobs are listed in rough order of priority: if multiple jobs fail, the first job
   # in the list should be the one that's most worth looking into
   build-linux:
+    if: (github.event.action == 'ready_for_review') || (github.event.pull_request.draft == false)
     uses: ./.github/workflows/run-mill-action.yml
     with:
       java-version: '11'
       millargs: __.compile
       populate_cache: true
 
   build-windows:
+    if: (github.event.action == 'ready_for_review') || (github.event.pull_request.draft == false)
     uses: ./.github/workflows/run-mill-action.yml
     with:
       os: windows-latest
@@ -41,6 +46,7 @@ jobs:
       populate_cache: true
 
   test-docs:
+    if: (github.event.action == 'ready_for_review') || (github.event.pull_request.draft == false)
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4